Emulsions of polyfluoroalkyl esters



United States Patent 3,121,688 EMULSIONS 0F POLYFLUOROALKYL ESTERS John J. Daly, 31"., and Alfred C. Haven, In, Wilmington,

Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Oct. 19, 1959, Ser. No. 847,111 3 Claims. (Cl. 25233.4)

This invention relates to stable water emulsions of polyfluoroalkyl esters of carboxylic acids which are particularly adapted for use as lubricants and coolants in the mechanical working of metals, and to the process of working metals in the presence of such emulsions.

For such metal working operations as milling, drilling, cutting, boring, reaming, tapping, threading, grinding and the like, lubricants are used in machine shops. A metal working lubricant of the aqueous emulsion type is preferred because it acts as both a lubricant to reduce friction and as a coolant to carry away heat. In metal working where a lubricant must primarily reduce friction, a non-aqueous oil is preferred, but, in many metal working operations, so much frictional heat is generated between the cutting tool and the surface of the metal being cut and between the cutting tool and the chip being removed, that cooling, as well as lubrication, must be provided. Heat of deformation from the bending of the chip is also a source of heat. Because aqueous emulsions contain large concentrations of water which has a higher specific heat and higher latent heat of vaporization than anhydrous oils, they are used whenever cooling is important.

A satisfactory cutting oil emulsion must be stable, that is, it must not separate into its component oil and water phases and must not become rancid or corrosive in storage or during use. It should provide the lubrication needed to attain a relatively low rise in temperature of the work. It should also leave an improved condition of finish on the work, particularly where precision and an otherwise tedious finishing operation area consideration. The cutting oil emulsion should protect the metal against rust and be harmless to an operator. It should, further more, be transparent and not mask the work from the vision of the operator.

A variety of cutting fluids is commercially available. The anhydrous oils, which mainly provide lubrication and are used in low speed operations where excessive heat is not generated, are generally mineral or fatty oils containing small amounts of sulfur, sulfurized or chlorinated hydrocarbons, or fatty acids as extreme pressure lubricant additives. For higher speed operations, water dispersions or emulsions of the oils are widely used to obtain cooling and lubricity. Aqueous emulsions of substances, which are lubricants when in anhydrous condition, often do not possess the required lubrication properties to allow working under such rigorous conditions as high speed, increased depth of cut and high feed rate. The emulsions may be unstable and corrosive after long periods of operation at high temperatures, cause failure of the cutting tool, spoil the appearance of the work, and contribute to other failures in the machine in which such lubricants are used. Various additives, to improve stability, reduce corrosion, and impart extreme pressure properties, may be introduced, but a multiple number of such additives may be required, and it is diflicult and costly to provide in one oil all of the properties that may be required for use with all metals. Extreme pressure additives tend to attack the metal being worked and the cutting tool. For example, sulfur-containing additives may so attack copper, tin, or zinc or alloys containing these metals that their use is deleterious, even though they may markedly improve the lubricity of the oils to which they are added.

Many esters of high molecular weight are known to have valuable lubricating properties, but form opaque or substantially opaque emulsions. A transparent emulsion is more desirable as a cutting fluid as it enables the operator to readily observe the progress of the work and the condition of the cutting tool without interrupting the operation. An opaque emulsion renders it more difficult for the operator to view the operation, and it may be necessary to shut down the machine and remove the emulsion from the surface of the work and the tool in order to check the progress of the operation and the condition of the tool, with resultant loss of time and production.

It is an object of this invention to transparent aqueous emulsions of polyfluoroalkyl esters of carboxylic acids. Another object is to provide an emulsion of the above character which is particularly suitable for use as a lubricant and coolant for metal working operations. A further object is to provide an improved process for the mechanical working of metals by employing as the lubricant and coolant an emulsion of the above character. A still further object is to so irnprove a metal working process as to produce an improved, smooth surface on the metal without causing objectionable corrosion or discoloration of the metal. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accordance with this invention which comprises stable emulsions of from about 1% to 10% by weight of at least one ester which contains at least 20 carbon atoms and has the formula R(CO0CH (CF ),,X) wherein R contains 1 to 12 carbon atoms and is a member of the group consisting of hydrocarbon radicals and halogenated aromatic hydrocarbon radicals, n is an integer of from 2 to 10, X is a member of the group consisting of hydrogen and fluorine, and m is an integer of 1 to 4, and which ester has a refractive index (11 of less than 1.4100, in water containing from about 0.1% to about 1% by weight of at least one anionic emulsifying agent of the group consisting of alkyl sodium sulfates containing 10 to 18 carbon atoms, sodium alkyl benzenesulfonates in which the alkyl groups contain 12 to 18 carbon atoms, sodium alkyl naphthalenesulfonates in which the alkyl groups contain 1 to 4 carbon atoms, sodium salts of sulfated alkenylacetates in which the alkenyl groups contain 16 to 18 carbon atoms, the sodium salt of sulfated methyloleate, ammonium wH-polyfluoroalkanoates of 8 to 10 carbon atoms and ammonium perfiuoroalkanoates of 8 to 10 carbon atoms. These emulsions are particularly adapted for use as lubricants and coolants in the mechanical working of metals and hence a further feature of this invention comprises the process of mechanical working of metals while applying to the surface of the metal being worked as a lubricant and coolant an emulsion as above defined.

The emulsions as above defined are stable when stored provide novel, stable,

and when used in metal working operations for long periods of time. They are transparent, at least in layers of 5 mm. thickness, so that, when they are employed in metal working operations, the operator can observe the progress of the operation easily, follow what is being done, and check the condition of the metal cutting tool without interrupting the metal working operation. They have high lubricating qualities and when used in metal cutting operations cause the surface of the metal to have an improved smooth finish. They undergo a minimum of steaming and smoking during metal working operations and possess sufiicient lubricating properties as to make unnecessary the addition of an extreme pressure agent. They are substantially non-corrosive to the metals and do not cause discoloration or other objectionable effects on the appearance of the metal. The esters in the emulsions are highly resistant to hydrolysis and oxidation under conditions of storage and under the conditions involved in metal working operations. Also, the esters of this invention have a sufiiciently low vapor pressure so that they do not volatilize from the emulsions during storage or under the conditions employed in metal working operations.

The esters of this invention have the formula wherein R is a hydrocarbon radical or a halogenated aromatic hydrocarbon radical of 1 to 12 carbon atoms, In is an integer of 1 to 4, n is an integer of from 2 to 10, and X is hydrogen or fluorine, preferably hydrogen, which esters contain a total of at least carbon atoms and have a refractive index (n of less than 1.4100. Esters which do not fall Within the limits above set forth do not have the desired properties for the purposes of this invention. They do not form emulsions having the necessary lubricity and/or transparency required. For example, the C -C polyfluoroalkyl esters of the (l -C carboxylic acids do not produce emulsions having the desired lubricity. Esters, whose refractive index is greater than 1.4100, such as the C C polyfluoroalkyl esters of oleic acid, produce emulsions which are opaque fluids.

The radical R in the formula R(COOCH (CF ),,X) may be a halogenated aromatic hydrocarbon radical, that is, an aromatic hydrocarbon radical in which one or more of the hydrogen atoms has been replaced by a halogen atom having an atomic weight of from about 19 to about 80, i.e., fluorine, chlorine or bromine. However, R usually will be a hydrocarbon radical, particularly a cyclic hydrocarbon radical of 6 to 8 carbon atoms and may be alicyclic, such as cyclohexyl and alkyl substituted cyclopentyl as in camphoric acid, or an aromatic radical. Also, when R is a cyclic radical, m will preferably be an integer of 2 to 4, i.e., the ester will be a polyester of a polycarboxylic acid. Particularly desirable esters are the esters of the benzene polycarboxylic acids wherein R is a benzene radical and m is an integer of 3 to 4, and especially of the benzene tetracarboxylic acid, pyromellitic acid, wherein R is a benzene radical and m is 4.

In general, the esters of this invention are known compounds. They are prepared by conventional esterifying processes well known to those skilled in the art. Some of the esters of this invention are disclosed by Faurote et al. on pages 445 to 454 of Industrial and Engineering Chemistry, vol. 48, No. 3, March 1956. The polyfluorodialkyl esters of camphoric acid, which constitute a valuable group of esters of this invention, and the processes of making them are disclosed by Sommers and Sturgis in Patent No. 2,840,593. The preferred class of esters of this invention, the neutral polyesters of the benzene tricarboxylic acids and tetracarboxylic acids, particularly of pyromellitic acid, and the mixtures of esters obtained from mixtures of 1H,lH,wH-polyfiuoroalkanols and such benzene polycarboxylic acids are disclosed by Donald R. Baer and Charles D. Ver Nooy III in their copending application Serial No. 699,930, filed December 2, 1957, now Patent No. 3,004,061. Faurote et al., Sommers et al., and Baer et al. disclose such esters to be valuable lubricants for use at high temperatures in anhydrous condition. They also disclose some esters of the present invention to be unsuitable for use as high temperature lubricants because of volatility or instability. However, such of those esters as fall within the scope of the present invention have sufficiently low vapor pressures and are sufiiciently stable for use in the form of aqueous emulsions in metal working operations.

The alcohols, employed for making esters and polyesters of this invention, include the polyfiuoroalcohols having the formula H(CF CF ),,CH OH wherein n is an integer of from 1 to 5, preferably from 1 to 4. These polyiluoroalcohols are known as telomer alcohols and are readily prepared, as described by Robert M. Joyce, Jr., in Patent No. 2,559,628, from tetrafiuoroethylene and methanol by a telomerization process which comprises heating a mixture of tetrafluoroethylene and methanol in the presence of a peroxy or an azo catalyst. This telomerization process produces a series of alcohols which contain at least one CF CF unit per molecule of methanol, including the alcohols employed to prepare the esters of this invention. Mixtures of the desired telomer alcohols are readily and economically manufactured by the process of Joyce. The use of such mixtures of telomer alcohols in the preparation of the polyesters produces mixtures of polyesters which have particularly desirable advantageous properties, and such mixtures of polyesters constitute preferred embodiments of this invention. The telomer alcohols, employed in making esters of this invention, include 1H,lH,3H-tetrafluoro-l-propanol (C 1H,1H,5H-octafluoro-l-pentanol (C 1I-l,1H,7H-dodecafluoro-l-heptanol (C 1H,lH,9H-hexadecafluoro-1- nonanol (C 1H,1H,11H-eicosafiuoro-l-undecanol (C and mixtures of any two or more thereof.

The 1H,lil-polyfluo-roalkanols which may be employed to form the esters of this invention and the method of making such polyfluoroalkanols are disclosed by Husted and Ahlbreoht in Patent No. 2,666,797. Representative alkanols of this class are 1H,lH-pentafiuoro-l-propanol (C 1H,ll-I-heptafluoro-l-butancl (C 1H,1H-undecafluoro-l-hexanol (C 1H,lfi-pentadecafiuoro-l-octanol (C and 1H,ll-l-nonadecailuoro-l-decanol (C Mixtures of the polyfiuoroalkanols that are particularly useful in the ester formation are, for example,

C C C C and C 1H,1l-LwH-polyfiuoroalkanols C C C and C 1H,lH,wH-polyiluoroalkanols C C and C 1H,ll-Lwl-l-polyfiuoroalkanols C and C 1H,1H,wl l-pclyfluoroalkanols C and C 1H,1H,wH-polyfiuoroalkanols C C C and C 1H,lH-polyfiucroalkanols C C and C 1H,lH-polyfiuoroalkanols C and C 1H, IH-polyfluorcalkanols The carboxylic acids that compose the acid part of the polyiluoro-alkyl esters of cutting fluid compositions of the invention include the following:

Nonanoic acid (pelargonic) 3-e thylheptanoic acid Decancic acid (capric) Undecanoic acid Tetradecanoic acid (myristic) 1-rnethylcyclohexanecarboxylic acid 1,2,2-trirnethyl-1,3-cyclopentanedicarboxylic acid camiphoric 1,2,3,4-tetrahydro-1-naphthcic acid 2-nonenoic acid 10-undecenoic acid Succinic acid Glutaric acid Dimethylmalonric acid Adipic acid 3-1nethylglutaric acid Ethylsuccinic acid Pimelic acid 2-ethylglutaric acid Suberic acid 3-propylglutanic acid Azelaic acid 3,3-diethylglutaric acid Sebacic acid 1, l-cyclopropanedicarboxylic acid 1,2-cyclohexanedicarboxylic acid Cyclohexylmalonic acid o-Tolylacetic acid 3,4-dimethy-lbenzoic acid l-n-aphthoic acid Z-naphthoic acid 1bromo-2-naphthoic acid Phthalic acid Isophthalic acid 4-chlorophthal ic acid Tetrachlorophthalic acid Terephthalic acid Alpha-carboxytoluic acid 1,2,4-benzenetricarboxylic acid (trimellitic) 1,3,5-benzenetricarboxylic acid (trimesic) 1,2,3,4-benzenetetracarboxylic acid (mellophanic) 1,2,4,S-benzenetetracarboxylic acid (pyromelli-tic) 2-biphenylcarboxylic acid. 4-biphenylcarboxylic acid Some of the single esters, prepared from a single polyfluoroalk-anol and a single acid, are wax-like or crystalline solids. Such solid esters may be emulsified in \Water and the emulsions employed as metal cutting fluids in accord with this invention. However, such solid esters are less readily adapted for the formation of emulsions than the esters prepared from a mixture of polyfiuoroalkanols and a selected acid or from a mixture of isomeric acids and a given polyfluoroalkanol, which latter acids are usually liquids of varying viscosity depending upon the chain length and the amount of the dilferent polyfluoroalkanols in the mixture of polyfiuoroalkanols that are used to prepare the esters. A mixture of polyiluoroalkanols esteritied with a monocarboxylic acid yields a mixture of esters having a common group contributed by the acid A mix ture of polyfluoroalkanols reacted with a polycarboxylic acid yields a mixture of polyesters in which the separate esters usually contain polyfluoroalkyl groups of diiferent chain lengths. The mixtures of polyesters, prepared from a mixture of polyfiuoroalkanols and a polycarboxylic acid, are preferred fluid mixtures of this invention. The use of a mixture of polyiiuoroalkanols, particularly the 1H,1H,wH-polyfluoro-alkanols, as they are produced by the telomerization reaction without separation, is also an economical advantage in the formation of the mixtures of esters of this invention. A particularly preferred mixture of polyesters of this invention is the mixture of tetraesters of pyromell itic acid made with a mixture of 1H, 1H,5l-I-octafluoro-1-pentanol and 1H, 1H,7H-dodecafiuorol-heptanol, in which mixture each polyfluoroalkanol constitutes at least mole percent of the mixture of poly fiuoroalkanols, preferably an equimolar mixture of the two polyfluoroalkanols. Another particularly desirable mixture of polyesters is the mixture of tetraesters of pyrome-llitic acid made with a mixture of 1H,1H,3H- tetrafiuoro-lpropanol, 1H,1H,5H octafluoro-l-pentanol, 1H,IHJH-dodecafluoro-l-heptanol and 1H,1H,9H-hexadecafiuoro-l-nonanol, in which one of the polyfluoroalkanols constitutes from 10% to 90% of the mixture and the other three polyfluoroalkanols constitute the other 90% to 10% of the mixture. A preferred mixture of polyfluoroalkanols, to be used in making the latter mixture of tetraesters of pyromellitic acid, is that composed of about to about 40 mole percent of 1H,1H, SH-tetrafiuoro-l propanol, about to about mole percent of 1H,1H,5H-octafluoro-l-pentanol, about 15 to about 30 mole percent of 1H,1H,7H-dodecafiuoro- 1- heptanol and about 5 to about 20 mole percent of 1H,1H, 9H-hexadecafluoro-l-nonanol.

The emulsifying agents that can be employed for pre paring the emulsions of this invention are critical and consist of one or more anionic emulsifying agents of the group of alkyl sodium sulfates containing 10 to 18 carbon atoms, sodium alkyl benzenesulfonates in which the alkyl groups contain 12 to 18 carbon atoms, sodium alkyl naphthalenesulfonates in which the alkyl groups contain 1 to 4 carbon atoms, sodium salts of sulfated alkenylacetates in which the alkenyl groups contain 16 to 18 carbon atoms, the sodium salt of sulfated methyloleate, ammonium wH polyfiuoroalkanoates of 8 to 10 carbon atoms and ammonium perfluoroalkanoates of 8 to 10 carbon atoms. These materials are well known anionic surface active agents. By the use of such emulsifying agents in the proportion of from about 0.1% to about 1% by weight of the emulsion, about 10% by weight of the ester, stable emulsions are produced.

When fatty acid esters, such as sodium oleate and sodium stearate, were used as emulsifying agents, the dispersed phase separated from the emulsion during a few days standing. Cationic and non-ionic types of emulsifying agents were ineffective, that is, either no emulsion was formed or the dispersed phase settled or separated from the emulsion on standing. Also, in order to prepare a stable emulsion, it is essential to employ a mixer having a high speed cutting and shearing action, such as a Waring Blendor, and the dispersed ester should not exceed 10% by weight of the emulsion. Emulsions containing the ester in a concentration in excess of 10% by Weight, are unstable unless they are treated with a thickening agent such as methyl cellulose, and such treated emulsions are opaque and low in lubricity. The preferred emulsifying agents are the alkyl sodium sulfates which contain from 10 to 18 carbon atoms. Also, preferably, the emulsions will contain from about 1% to about 5% by weight of the ester, most preferably about 3% by Weight.

A satisfactory and convenient method for measuring the lubricity of the emulsions is the rapid Falex test described by E. G. Ellis in Lubricant Testing, 1953, page 153. Essentially, the test involves the failure of an emulsion to carry a load as evidenced by the seizure of the test pin and bushings or a sudden increase in torque reading. Such test method has been employed to determine the lubricity of the emulsions of this invention as shown in the examples given hereinafter.

In order to more clearly illustrate this invention, preferred modes of practicing it, and the advantageous results to be obtained thereby, the following examples are given in which the parts and proportions are by weight, except where specifically indicated otherwise.

EXAMPLE 1 Preparation of Representative Polyfluoroalkyl Ester Emulsion To 773 g. of water contained in a 1 gallon Waring Blendor was added an intimate mixture of 24 g. of the tetraester of pyromellitic acid, prepared with an equimolar mixture of 1H,1H,5H-octafluoro-1-pentanol and 1H, 1H, 7H-dodecatluoro-l-heptanol, and 2.4 g. of 4-ethyl-l-(3-ethylamyl)octyl sodium sulfate (supplied as the commercial product known to the trade as Tergitol No. 7). The mixture was stirred for 20 minutes with the blender turning at 16,000 to 18,000 r.p.m. A stable, transparent emulsion was obtained, containing about 3% by weight of the ester. After two weeks storage, a complete dispersion existed; no separation of the ester and water phases had occurred.

EXAMPLE 2 In the manner described in Example 1, the polyfiuoroalkyl esters listed in Table I were emulsified, employing proportions of ester and water to provide 1% and 5% emulsions, and a 50/50 mixture of tridecyl sodium sulfate and isodecyl sodium sulfate as the emulsifying agent in an amount equal to 16% by Weight of the ester. Emulsions of unsubstituted allryl esters, analogous to five of the polyfiueroalkyl esters, were simularly prepared An examination of the condition of the surface of the cut metals revealed the exceptional and unexpected performance of applicants emulsion. After each metal had been cut, the surface was measured for smoothness I 1 U 1 with a profilometer described in Metals Handbook, 1948 r 'r L v. for f g ii .g i he Edition, pa e 362. Actually, the roughness of the surcmu Slot} 0 E p y 1 a 6 es 1 O e was face of the metal was measured; the root mean square made with 4-eti1yl-1-(3-ethylamyl)octyl sodium sulfate as d i epth of the depressions was reg1stered on the urofilomthe emulsifying agent. t Tho ah C d d Tab: H 1 t The emulsions were examined for clearness by viewing 10 e re e m f 1 16 gas P l 0 them transversely m a 2.5 cm. diameter test tube and 101117 or smoolnest ace lmparted to of tested for lubricity by the Falex test. The results are thg five mfitals Wlth the pclyfiuol'oalkyl Pymmelhtate given in Table I. emulsion employed as a cutting fluid.

TABLE I Refractive Percent Falex Test Index of Conen. Data, Max. Ester ester of Appearance of Emulsion load at 11,, Emulfailure,

sion lbs.

. T 1 3 1 i l Tristan; i233 iester of -metl1y g utaric acid wit 1 1 :1 m0 ar mixture of1H,1H,7H-dodeeafluoro-l-lleptauol and 111,111,911- 1.3467 Tmfiffmnhclear hexadeeafiuore-Lnonanol. "0 2 00 Dinonylsluwmw 1-4445 l Elit 21600 e Diester 0i adipic acid With 1:1 molar mixture of 1H,lH,QH-hexadeeaflu0r0-1u10nau0l and 1H,1H,11H- liggi gggi gl g eieesafiuoro-l-uudecanel. ce i-l-ethylhexyladipate 1.4454 9 i ggi:::::::: d .1 Diester oi eamphorie acid with 1:221 molar mixture of 1H,1H,5H-octafluoro-l-pentanol, 1II,1H,7H- 1 1 Transparent, clear 1,925 dodeeal'luoro-l-heptanol and IHJILQILhBXQQQGa- 5 o 2,625 fluoro-1-nonanol. de,. Di-2-ethylhexyl campliorate 1.4662 r 1 Transparent elear 3:150 e 131s(1H,111,7H-d0decafluorol1eptyl)phthalate 1.3.503 5 Transparent: 51 3 9 ee Di-Z-ethylhexylphthalate 1.4849 do i338 Bis(1H,1H,7H-dodeeafluoroheptyl)4-ehler0phthalate 1.3917 Bis(1H,1H,7H-d0deeaflu0r0heptyl)tetraehlorophthalate 1 4, 500 Triester of trimellitic acid with 1:1 molar mixture of 1 2 1I-I,1H,5H-0etafluoro-Lpentanol and 1H,1H,7H-dode- 1 3839 5 r eafluoro-l-heptanol. Y" i 'Ietraester of pyromellitie acid With mixture of alkauols 1 3787 1 3, 900 used in h. 5 3,5550 10 Tetrabutyl pyromellitate 1.4878

I The lubricity of the relatively dilute transparent emul- TABLE H EFFECT OF CUTTING FLUID ON SURFACE sums of the poly-fluoroalkyl esters 15 excellent. In each FINISH or our METAL instance, where a comparison was made with an analogous [Surface finish in mieroinehes 1 measured by pi-ofilometerl alkyl ester, the lubricity of the poly fluoroalkyl ester emul- 5Q sion is definitely superior, and the clear transparent fluids St 4 M 1 A Sili- 1: I 1 L am- 1 one J'lllOI C011- 1 21- made wrth the polyiiuoroaliiyl esters are in sharp conuast Cutting Fluid less Metal steel Mum? mm with me opaque ali yl ester emulsions. Steel r EXAMPLE 3 55 3% Emulsion of polyfluero- 1 alkylpyromellitate 135 135 115 The 3% emulsion of tne polyfluoroalkyl pyromellitate 3.8% E 1nulsionefPreduetiL 345 395 305 37% described in Example 1 was evaluated as a cutting fluid in 4% kmulslon ofpmdmtB'" 260 235 U cutting different metal rods 2 inches to 3 inches in diameter m 1 h 1 th h dfi th fi h on a high spindle-speed engine lathe equipped with a cir- 0 em M an Her e culating cooling system from which the cutting fluid was The surface on the fifth metal, titanium, was about 15% f to the surface f the motel being out The m l w smoother with the emulsion of Product B than with the fed to a high speed steel cutting tool at the rate of 0.01 synthetic ester emulsion, While the surface of titanium inch per revolution, and the tool Was set to cut 0.05 i ch after cutting with the synthetic ester emulsion was 55% in depth. Comparison was made with two high grade 65 smother than with the emulsion of Product A. The imcommercial cutting fluids, designated A and B, on the efproved condition of the surface of the stainless steel, foot of th cutting fluid 0n surfaC finis A mu n Monel metal, armor steel and the silicon-aluminum alloy of 3.8% concentration of Product A and a 4% emulsion means th t h l grinding nd polishing are needed of Pmdllct B Wfife imployed in the tesis- Product A i in finishing these metals for subsequent use. This ima transparent deep red liquid and is said to contam a 70 proved diti i especially important when a piece of group of water-soluble long-chain polar compounds, bactericides, and extreme pressure chemicals. Product B is a yellow opaque liquid and is said to contain wetting agents, lubricants, corrosion inhibitors, water conditioners, and a bactericide.

metal must be cut to a uniformly precise measurement.

EXAMPLE 4 The 3% emulsion of the polyfluoroalkyl pyromellitate described in Example 1 was evaluated as a grinding fluid in grinding 4340 steel of Rockwell C hardness of 55. Rods of 2-inch diameter were fed to a grinding wheel (aluminum oxide abrasive) at a traverse rate of 3.2 in./ min. and the wheel was set to cut .003 inch in depth. The wheel speed was 1750 r.p.m. and the work was rotated at 100 rpm. in a direction opposite to that of the wheel. The grinder employed was equipped with a circulating cooling system, from which the fluid was fed to the wheel-work interface. Comparison of the effect of the pyromellitate emulsion on surface finish was made with an emulsion of Product B of Example 3, and was measured with the profilometer (described in Example 3).

TABLE III.EFFECT OF GRINDING FLUID ON SURFACE FINISH OF 4340 STEEL [Surface finish in mici-oinches 1 measured by profilometer] 3% emulsion of polyfluoroalkyl pyromellitate 2 4.8 3.3% emulsion of Product B 2 7.5

1 The lower the value the smoother the finish.

2 Average of values obtained in three runs.

As shown in the above table, the finish produced when Product B was used as the grinding fluid was 55% poorer than when the fluoroester emulsion was used. This means that a superior precision grinding can be obtained with the latter emulsion.

EXAMPLE Oxidation and Heat Stability of Polyfluoroolkyl Pyromellitate Emusion and Efiect on Metals A 100 g. portion of the pyromellitate ester emulsion described in Example 1 was heated at 70 C. for 19 days with air constantly bubbling through the emulsion, and immersed in the emulsion were about 18 x 12 X 3 mm. test pieces of aluminum, brass, titanium, and No. 1020 hot rolled steel. At the end of the heating period, the emulsion was still essentially colorless and otherwise showed very little change.

Also, after the heating, none of the metals was discolored or changed in appearance except the aluminum which was slightly pitted. The measured loss in weight of the metals was:

Loss of weight of metal in mg.

Aluminum "2.1 Brass 3.3 Titanium 0.1 Steel 1.2

The loss in weight of similar test pieces heated in the same manner in a control 3 sodium oleate solution was:

Loss in weight in mg.

Under these oxidative conditions over the prolonged period, the polyfluoroalkyl pyromellitate cutting fluid is considered to have no effect on titanium and steel, a very slight corrosive action on aluminum and brass, and less effect on brass than a sodium oleate solution.

In a 5% emulsion, the mixed pyromellitate ester of Example 1 hydrolyzed to the extent of only 0.6% during 30 days at room temperature and only 2.5% after 16 days at 160 F. Also, in a 5% emulsion, the camphorate ester ((1) of Table 1, Example 2, the hydrolysis was less, being 0.05% and 0.4% respectively for these conditions.

In addition to their use as metal working lubricants, the emulsions of this invention are also useful as textile treating agents, water proofing agents, hydraulic fluids,

1% and for other purposes which will be apparent to those skilled in the art.

It will be understood that the preceding examples have been given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it will be readily apparent that, within the limitations set forth in the general description, many variations and modifications can be made in the materials, the proportions, the conditions and the techniques employed without departing from the spirit or scope of this invention.

From the preceding description and examples, it will be apparent that this invention provides stable transparent emulsions which are novel and are valuable for a variety of uses and purposes. Such emulsions are particularly adapted and valuable for use as metal working fluids and when so used provide substantially improved results, particularly in providing a smoother surface on the metal worked and enabling the operator to observe the progress of the work and the condition of the metal working tool without interrupting the metal working operation. Accordingly, it is apparent that this invention constitutes a valuable contribution to and improvement in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

We claim:

1. A stable transparent emulsion of from about 1% to 10% by weight of a mixture of polyesters each of which contains at least 20 carbon atoms and has the formula R(COOCH (C-F ),,H) wherein R is a benzene radical, it is an integer of from 2 to 10, and m is an integer of 3 to 4, and which ester has a refractive index (r1 of less than 1.4100, in water containing from about 0.1% to about 1% by weight of at least one alkyl sodium sulfate containing 10 to 18 carbon atoms as an emulsifying agent.

2. A stable transparent emulsion of from about 1% to about 5% by weight of a mixture of neutral polyesters of pyrornellitic acid and a mixture of alcohols of the class having the formula H(CF CH OH wherein n is an integer of from 2 to 10, in water containing about 1% by weight of at least one alkyl sodium sulfate containing 10 to 18 carbon atoms as the emulsifying agent.

3. A stable transparent emulsion of from about 1% to about 5% by weight of a mixture of neutral polyesters of pyro-mellitic acid and about an equimolecular mixture of 1H,1H,5H-octafluoro-1-pentanol and 1H,1H,7H-do decafiuoro-1heptanol, in water containing about 1% by weight of at least one alkyl sodium sulfate containing 10 to 18 carbon atoms as the emulsifying agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,559,629 Berry July 10, 1951 2,840,593 Sommers et a1 June 24, 1958 2,921,957 ORear et a1. Jan. 19, 1960 3,004,061 Baer et al Oct. 10, 1961 OTHER REFERENCES Faurote et al.: Partially Fluorinated Esters and Ethers as Temperature-Stable Liquids, I. and E. Chem, vol. 48, No. 3, March 1956, pages 445-454.

Synthetic Detergents, Soap and Sanitary Chemicals, August 1952, pages 56 and 59.

Handbook of Material Trade Names, Zimmerman et al., 1953 Edition, page 561.

"Metal Working Lubricants, Bastian, pub. by McGraW- Hill, New York, N.Y., 1951, page 22. 

1. A STABLE TRANSPARENT EMULSION OF FROM ABOUT 1% TO 10% BY WEIGHT OF A MIXTURE OF POLYESTERS EACH OF WHICH CONTAINS AT LEAST 20 CARBON ATOMS AND HAS THE FORMULA R(COOCH2(CF2)NH)M WHEREIN R IS A BENZENE RADICAL, N IS AN INTEGER OF FROM 2 TO 10, AND M IS AN INTEGER OF 3 TO 4, AND WHICH ESTER HAS A REFRACTIVE INDEX (ND25) OF LESS THAN 1.4100, IN WATER CONTAINING FROM ABOUT 0.1% TO ABOUT 1% BY WEIGHT OF AT LEAST ONE ALKYL SODIUM SULFATE CONTAINING 10 TO 18 CARBON ATOMS AS AN EMULSIFYING AGENT. 